1. Field of the Invention
The invention relates to a transport system for transporting workpieces from a machining station into the next machining station in a press, press line, or the like.
2. Related Art
Where the manufacture of a workpiece calls for a plurality of work operations, for the economic production of the sheet-metal part, the necessary individual operations are carried out in a transfer press or press line, as they are known. The number of dies then correspond to the number of work stages which are necessary for the manufacture. Transfer presses of this type have a transport device with which the workpieces are transported onward from one workstation to the next.
As a rule, such transport devices are nowadays equipped with loadbearing rails which extend through the entire length of the shaping machine. In order to transport the components, the loadbearing rails are fitted with gripper or holding elements. In this case, a distinction is made, depending on the movement sequence, between a two-axis transfer fitted with suction crossmembers or a three-axis transfer provided with gripper elements. As an additional movement, pivoting in order to change the attitude of the component during the transport step may also be required.
The transfer movement is initiated via cams, which are forcibly synchronized with the ram drive via movement transmission elements. The manufacture or large-area components, in particular, has led to the development of large-component transfer presses of greater and greater dimensions, based on the shaping force and the transport paths. Die spacings of the order of magnitude of 3000 mm are entirely normal nowadays, and therefore corresponding transport steps are also necessary.
As a result of this development, the masses to be accelerated and braked in the transfer systems are completely opposed to the low masses of the components to be transported.
A further disadvantage is the rigid movement sequence which is predefined by the cam drives. In the event of a changeover to a new workpiece, it would generally also be necessary for the transfer cams to be adapted.
In order to avoid these indicated disadvantages, intellectual rights applications nowadays concern the replacement of the previous transfer system by a corresponding number of transfer systems arranged between the machining stages and equipped with their own drive. Such an arrangement is disclosed by EP 0 672 480 B1. Transfer systems arranged on the uprights are equipped with a number of drives which, in operative connection with the movement transmission means, carry out the transport of the components. As a special feature, the system can be re-equipped both as a two-axis transfer with suction beams and as a three-axis transfer with grippers. However, this universal use requires a corresponding outlay on construction.
Likewise arranged in each upright area is a transfer device disclosed by DE 196 544 75 A1. In this application, elements which are known asxe2x80x94parallel kinematicsxe2x80x94are used for the drive. In a modification of these known movement elements, however, telescopic lengthening of the drive rods is not performed, but, with a constant rod length, the attachment points are changed and therefore the transport movements are achieved. The attachment points that accommodate the forces or torques are not constant in terms of their distance from one another and, in particular when these points are close to one another because of the desired travel curve, support problems can occur. In order to increase the stiffness of the system, further mutually parallel links are also proposed, which are connected to one another by transverse crossmembers. In order to achieve functionally reliable transport of large-area components, the proposed system becomes correspondingly complicated.
U.S. Pat. No. 5,452,981 has disclosed a device for transporting workpieces according to the preamble of claim 1. In this case, the device operates with a threaded spindle, which firstly has a poor efficiency and therefore a not inconsiderable power loss. Furthermore, such drives are sluggish and cannot do justice to a highly dynamic drive mode.
An object of the invention is based upon the fact that, by using simple measures, of providing a highly flexible and precise transport system which, irrespective of the respective transport attitude, ensures uniformly safe support for the forces and torques which occur.
The invention is based on the idea that, by controlling the rotational speed and direction of rotation of two drives in relation to each other, and in operative connection with movement transmission means, any desired two-axis movements in the horizontal and/or vertical direction are possible. In this case, two highly dynamic drives are controlled by means of simple control operations which influence the direction of rotation and the rotational speed. As a result of superimposing movements in the X and Y axis, this control produces any programmed travel curve in one plane.
If the movement transmission means used is a rack or toothed belt drive, the introduction of the travel curve onto a pivoting or transport arm being carried out via a gear, then the uniform support for the torque is therefore also ensured by the unchangeable gear diameter. The respective movement position does not lead to any kind of change in the effective lever arm relating to the introduction of torque or to the support, and therefore ensures safe and precise component transport.
The above and other objects are accomplished according to the invention by provision of a transporting device for transporting workpieces in a press. The transporting device can include a pivoting or transport arm, a load-bearing carriage for carrying the pivoting or transport arm that is movable in a longitudinal direction, a drive gear for rotating the pivoting or transporting arm, two racks arranged in parallel for acting jointly on the drive gear, at least two stationary drive motors for driving the two racks, respectively, the drive motors being controllable in direction of rotation, speed of rotation, and stopping for affecting a coordinated movement of the two racks for setting the longitudinal movement of the load-bearing carriage and the rotating of the pivoting or transport arm. In such a transporting device, the rotation direction and speed of rotation coordinate movement of the two racks and the longitudinal movement of the load-bearing carriage and the rotating of the pivoting or transport arm are set.
In a further embodiment, a transporting device for transporting workpieces in a press is provided in which the transporting device includes a pivoting or transport arm, a load-bearing carriage for carrying the pivoting or transport arm that is movable in a longitudinal direction, a drive gear for rotating the pivoting or transporting arm, at least two stationary drive motors for driving the two toothed belt, respectively, the drive motors being controllable in direction of rotation, speed of rotation, and stopping for affecting a coordinated movement of the two toothed belt drives for setting the longitudinal movement of the load-bearing carriage and the rotating of the pivoting or transport arm. In such a transporting device, the rotation direction and steed of rotation coordinate movement of the two racks and the longitudinal movement of the load-bearing carriage and the rotating of the pivoting or transport arm are set.
Depending on the objective, the transport system, in a single design or in a double design, can be fitted in mirror-image fashion in relation to each other, in each case transversely with respect to the press transport direction in the upright area. In the case of use in pairs, the two transport systems are connected, for example by a suction beam carrying the components. Of course, in the case of double-component production, each transport device can also have its own suction beam supported on one side, and the transport systems can be driven independently of each other. Synchronization of the component transport device with the press rail can be carried out with known electronic means, such as the so-called electronic shaft.
Travel curves determined in simulation operation, for example, for the individual transport stages can be configured flexibly, in particular on the basis of the shaping of the components and of the ram position. An advantage which results from this is optimum utilization of the degrees of freedom and, by means of time-offset shaping in the individual press stages, favorable distribution of the press drive power.
If intermediate storage is dispensed with, or for reasons of component transport, pivoting of the suction crossmember can be provided as an additional movement. By means of a simple construction of the transport device proposed, the incorporation of the additional pivoting movement is possible without problems and with only a small change in mass.
The position in which the transport system is added on is variable and may, for example, be carried out above or below the component transport plane. Weight compensation measures, for example by means of the addition of cylinders, both on the actual travel carriage and also on the transport arm lead to the load being relieved on the drives and the movement transmission means. The distance between the shaping stages, predefined by the design structure of the press is not increased by the narrow design of the transport system. On the other hand, in spite of this space-saving design, long transport paths can be executed without problems, with low mass and with great precision.